As well known in the art, there is a system controlled by a plurality of policies (operation policies) (policy-based control). In such a system, contents of the policies are specified so as not to conflict with each other. Therefore, upon changing a policy for the system, the policy needs to be changed so that the policies do not become conflictive with each other due to such a policy change.
Such a policy in the system using the policy-based control is almost the same as a control program to the system. Therefore, if any policies are incorrect (have any conflict), the system operates according to the incorrect way specified in the policy. Therefore, it has been necessary to validate whether policies are appropriate in advance (before implementing a policy change), and various efforts have been made.
For example, E. C. Lupu, M. S. Sloman (“Conflicts in Policy-Based Distributed Systems Management”, IEEE Transactions on Software Engineering—Special Issue on Inconsistency Management, 1999), and Nicole Dunlop, Jadwiga Indulska, Kerry Raymond (“Dynamic Conflict Detection in Policy-Based Management Systems”, 2002) suggest methods for validating that there is no conflict among a plurality of policies, and that the policies are appropriate in advance. In addition, E M Clarke, O. Grumberg, and D. Peled (Model Checking. MIT Press, 1999) suggest a method such as model detection. In this model detection, to validate whether policies are appropriate, it is examined whether a target condition is achieved by allowing a system to be controlled by the policies. Furthermore, because such validations generally require a large amount of calculations, Nicole Dunlop, Jadwiga Indulska, Kerry Raymond (“Dynamic Conflict Detection in Policy-Based Management Systems”, 2002) described above suggest a method for performing validations in advance, or addressing this issue dynamically by reducing the amount of calculation by devising formulas used for validations.
In addition to these technologies, other suggestions have been made. Such suggestions include a method for correcting a decision rule tree (Japanese Laid-open Patent Publication No. 2000-155680, pages 1 to 3, FIG. 3). In this method, upon correcting a decision rule tree, instead of correcting each and every parameter, the decision rule tree is gone back from an incorrect decision rule to a branch that leads to a correct decision, and correcting only decision rules belonging to that branch. Another suggestion includes a method for reducing a size of a computer program used for validating input information, by performing any one of changing and adding or both against definitions for validating the input information (Japanese Laid-open Patent Publication No. 2005-311654, pages 1 to 4, FIG. 2).